Conventionally, composites that use three-dimensional fabric (three-dimensional fiber structure) as reinforcing material have been proposed as fiber-reinforced composites, which are widely used as light structural material. The fiber-reinforced composites have extremely high strength, and are used as part of structural material of, for example, aircraft. As a method for producing the three-dimensional fiber structure used in the reinforcing material of the fiber-reinforced composites, a method has been proposed in which a fiber bundle lamination is formed by laminating fiber bundle layers, each of which is formed by folding back a fiber bundle, to be at least biaxially oriented, and the fiber bundle lamination is connected by a thickness direction thread arranged perpendicular to the fiber bundle layers. Patent Documents 1 and 2 each disclose a fiber bundle arranging device that forms fiber bundle layers by feeding a fiber bundle from a guide pipe, which moves along an arranging surface, and arranging the fiber bundle to be folded back and forth between pins arranged at a predetermined pitch in a state where the fiber bundle is flat and the flat surface of the fiber bundle is arranged along the arranging surface.
From the aspect of the physical property of the three-dimensional fiber structure, the fiber density of the fiber bundle is preferably high. To increase the fiber density of the fiber bundle, fiber bundle array engaged with the pins may be depressed toward the roots of the pins in the vicinity of the pins. For example, depression means including a press plate and a pair of press blocks as disclosed in Patent Document 1 has been proposed as a depressing mechanism. The press plate and the pair of press blocks have lengths substantially equal to the length of the array of pins arranged in one direction. The press plate and the pair of press blocks press the fiber bundle at once along the entire length of the array of pins.
However, since the depression means disclosed in Patent Document 1 has the length substantially equal to the length of the array of pins, the fiber bundle arranging device is disadvantageously large.
Furthermore, the depression means disclosed in Patent Document 1 is not placed at the position where pressing operation should be performed while the fiber bundle is being arranged. Thus, the depression means needs to be placed at the position where pressing operation should be performed after arranging the fiber bundle corresponding to one layer of the fiber bundle layers. With this procedure, however, time is taken to form the fiber bundle layers including the pressing operation.
Patent Document 1: Japanese Laid-Open Patent Publication No. 8-218249
Patent Document 2: Japanese Laid-Open Patent Publication No. 2007-16347